From: Jiri Olsa <jolsa@redhat.com>
Date: Tue, 4 Jan 2022 13:10:30 +0100
Subject: bpf/selftests: Fix namespace mount setup in tc_redirect
Patch-mainline: v5.17-rc1
Git-commit: 5e22dd18626726028a93ff1350a8a71a00fd843d
References: jsc#PED-1377
The tc_redirect umounts /sys in the new namespace, which can be
mounted as shared and cause global umount. The lazy umount also
takes down mounted trees under /sys like debugfs, which won't be
available after sysfs mounts again and could cause fails in other
tests.
# cat /proc/self/mountinfo | grep debugfs
34 23 0:7 / /sys/kernel/debug rw,nosuid,nodev,noexec,relatime shared:14 - debugfs debugfs rw
# cat /proc/self/mountinfo | grep sysfs
23 86 0:22 / /sys rw,nosuid,nodev,noexec,relatime shared:2 - sysfs sysfs rw
# mount | grep debugfs
debugfs on /sys/kernel/debug type debugfs (rw,nosuid,nodev,noexec,relatime)
# ./test_progs -t tc_redirect
#164 tc_redirect:OK
Summary: 1/4 PASSED, 0 SKIPPED, 0 FAILED
# mount | grep debugfs
# cat /proc/self/mountinfo | grep debugfs
# cat /proc/self/mountinfo | grep sysfs
25 86 0:22 / /sys rw,relatime shared:2 - sysfs sysfs rw
Making the sysfs private under the new namespace so the umount won't
trigger the global sysfs umount.
Reported-by: Hangbin Liu <haliu@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jussi Maki <joamaki@gmail.com>
Link: https://lore.kernel.org/bpf/20220104121030.138216-1-jolsa@kernel.org
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/testing/selftests/bpf/prog_tests/tc_redirect.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/tools/testing/selftests/bpf/prog_tests/tc_redirect.c
+++ b/tools/testing/selftests/bpf/prog_tests/tc_redirect.c
@@ -105,6 +105,13 @@ static int setns_by_fd(int nsfd)
if (!ASSERT_OK(err, "unshare"))
return err;
+ /* Make our /sys mount private, so the following umount won't
+ * trigger the global umount in case it's shared.
+ */
+ err = mount("none", "/sys", NULL, MS_PRIVATE, NULL);
+ if (!ASSERT_OK(err, "remount private /sys"))
+ return err;
+
err = umount2("/sys", MNT_DETACH);
if (!ASSERT_OK(err, "umount2 /sys"))
return err;